W610 AJR:187, December 2006 AJR 2006; 187:W610–W617 0361–803X/06/1876–W610 © American Roentgen Ray Society M E D I C A L I M A G I N G A C E N T U R Y O F Esteves et al. Parameters for Interpreting MAG3 Renography Genitourinary Imaging • Original Research 99m Tc-MAG3 Renography: Normal Values for MAG3 Clearance and Curve Parameters, Excretory Parameters, and Residual Urine Volume Fabio P. Esteves 1 Andrew Taylor 1 Amita Manatunga 2 Russell D. Folks 1 Meghna Krishnan 1 Ernest V. Garcia 1 Esteves FP, Taylor A, Manatunga A, Folks RD, Krishnan M, Garcia EV Keywords: camera-based MAG3 clearance, genitourinary tract imaging, kidney, MAG3 normal values, nuclear medicine, renal uptake of MAG3, urinary tract DOI:10.2214/AJR.05.1550 Received September 1, 2005; accepted after revision November 8, 2005. Supported by grant ROI LMN07595 from the National Library of Medicine. 1 Department of Radiology, Division of Nuclear Medicine, Emory University Hospital, 1364 Clifton Rd. NE, Atlanta, GA 30322. Address correspondence to A. Taylor. 2 Department of Biostatistics, Emory University School of Medicine, Atlanta, GA. WEB This is a Web exclusive article. OBJECTIVE. Specific quantitative measurements have been recommended to assist in the interpretation of technetium-99m mercaptoacetyltriglycine (MAG3) renal studies. Our objec- tive was to define the sex- and age-specific normal ranges for these recommended parameters. MATERIALS AND METHODS. Data were obtained from a retrospective analysis of 106 subjects who were evaluated for kidney donation. The MAG3 clearance was calculated us- ing a common camera-based method. The relative uptake, prevoid/postvoid and postvoid/max- imum count ratios were determined using whole-kidney regions of interest (ROIs). Time to peak, time to half-peak, 20 min/maximum and 20 min/2–3 min count ratios were determined for cortical and whole-kidney ROIs. Residual urine volume was calculated on the basis of the pre- and postvoid bladder counts and voided urine volume. RESULTS. The mean camera-based MAG3 clearance was 321 ± 69 mL/min/1.73 m 2 , es- sentially the same as the mean plasma sample MAG3 clearance in comparable populations. The percentages of relative uptake in the right and left kidneys were 49% and 51% ± 4%, respec- tively; no difference was seen between men and women. Cortical values were lower than the whole-kidney values (p < 0.001); the mean cortical 20 min/maximum count ratio was 0.19 (SD, 0.07 and 0.04 for right and left kidneys, respectively). The mean postvoid/maximum whole- kidney count ratio was < 0.1, and the mean postvoid residual bladder volume was < 30 mL. CONCLUSION. Normal limits adjusted for age and sex have been established. Applying normal ranges to quantitative MAG3 parameters may assist in the interpretation of MAG3 scin- tigraphy and facilitate appropriate patient management. he use of technetium-99m mer- captoacetyltriglycine (MAG3) has increased significantly since its introduction in 1986 [1, 2]. Be- cause of the favorable imaging characteristics of 99m Tc and the more efficient renal extrac- tion of 99m Tc MAG3 compared with 99m Tc di- ethylenetriaminepentaacetic acid (DTPA), 99m Tc MAG3 has become the radiopharma- ceutical of choice in many clinical contexts, particularly for patients with suspected ob- struction or impaired renal function [3–6]. Today, 99m Tc MAG3 is estimated to be used in approximately 70% of the 590,000 renal scans obtained annually in the United States, but many renal scans are interpreted by diag- nosticians in sites that perform fewer than three studies per week [4, 7]. Clearance measurements and other spe- cific quantitative parameters have been rec- ommended to assist in scan interpretation and patient management [8–13]. For example, to assist in the interpretation of angiotensin-con- verting enzyme inhibition renography, the Santa Fe consensus report [14] and the Soci- ety of Nuclear Medicine procedure guideline on renovascular hypertension [15] recom- mend measurements of time to maximum counts (Tmax) and 20 min/maximum (20 min/max) count ratios for whole-kidney and cortical regions of interest (ROIs). The 20 min/2–3 min count ratio has been proposed as a useful parameter to simultaneously evaluate clearance and excretion, and it may be espe- cially useful in monitoring transplantation pa- tients to distinguish between acute tubular ne- crosis and rejection [16]. A measurement of urine drainage based on a quantitative com- parison of postvoid kidney counts with the counts obtained during the prevoid period im- proves the sensitivity and specificity for de- tecting an obstructed kidney [17–19]. Finally, the postvoid urine volume can easily be deter- mined at the time of scanning and may pro- vide important additional information regard- ing excretory function [20]. T